Scientists investigating the killing of at least 33 seals whose mutilated bodies have washed ashore in Norfolk and the surrounding coastline say they believe the deaths were caused by a vessel with a ducted propeller that has caused “corkscrew-style” mutilations on the seals’ bodies, BusinessGreen.com reported Tuesday.

A scientist at St. Andrews University Seal Mammal Research Unit says vessels operating between the Sheringham Shoal wind farm and Wells Harbor in North Norfolk might be the cause.

“Wind farms per se are not to blame,” Callan Duck said. “It’s possible that some of the vessels involved in wind farm construction might be responsible, but we do not know that for sure.”